Magnetic core shift register



Oct. l, 1968 Filed May 27, 1965 YVES-JEAN F. BRETTE ET AL MAGNETIC CORE SHIFT REGISTER NCR NBN.L

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5 Sheets-Sheet l Oct. 1, 1968 vYvEs-JEAN F. BRETTE ETAL 3,404,390

MAGNETIC CORE SHIFT REGISTER Filed May 27, 1965 3 Sheets-Sheet 2 Oct. 1, 1968 YVES-JEAN F. BRETTE ET AL. 3,404,390

MAGNETIC CORE SHIFT REGISTER Filed May 27, 1965 5 Sheets-Sheet 3 FIGA Q United States Patent O 2 claims. (Cl. 340-174) The present invention relates to a magnetic core shift register comprising neither diodes nor capacitors in the electric transfer circuits between the cores of successive stores.

In the known shift registers of this type, each transfer circuit comprises a Winding supported by an auxiliary saturable magnetic core and consequently has a self inductance which depends both upon the direction of the current ilowing through it and upon the direction of the residual induction in the auxiliary magnetic core.

The direction of the residual induction in the auxiliary magnetic core of each transfer circuit is so established before each shift operation that one transfer circuit has a low inductance with respect to a current flowing through this circuit, so as to effect a transfer of information, While the succeeding transfer circuit has a high inductance with respect to the current which is generated in this circuit by the induced electromotive force, by reason of the said transfer of information, and which would prevent this transfer if it were not appropriately limited. The necessary limitation -of this current results from the reversal of the direction of the residual induction in the auxiliary magnetic core of the latter transfer circuit. H-owever, the initial direction of the residual induction in the said auxiliary magnetic core can only be restored before the succeeding shift operation by means of certain particular means which are attended by various disadvantages and require the maintenance of narrow tolerances in the dimensions of the cores, in their characteristics and in the value of the control currents employed.

One object of the invention is to obviate these disadvantages.

In accordance with the invention, these disadvantages of the aforesaid shift registers are obviated by employing auxiliary magnetic cores having low residual induction and by providing means for modifying the magnetic permeability of these cores.

More particularly, the invention `concerns a shift register comprising magnetic storage cores having high residual induction, which is characterised in that each transfer circuit between two successive storage cores comprises a winding supported by an auxiliary magnetic core having low residual induction, and in that a portion of such a -core is divided into two parallel branches of like cross-section and supports a winding by means of which, when a current of appropriate value flows therethrough, the said portion can be brought to the state of magnetic saturation and the flux through any cross-section of the said core may be zeroised.

Such a shift register according to the invention is also characterised in that, considering one storage core -of the register, the transfer circuit for the transfer of information from this storage core to the next core and the auxiliary magnetic core associated with this transfer circuit, the dimensions and the magnetic characteristics of the storage core under consideration and those of the auxiliary core under consideration are so chosen that the value of the current which produces in the auxiliary core under consideration a ilux equal to the flux variation produced in the storage core under consideration by the reversal of the direction of the residual induction in the 3,404,390 Patented Oct. 1, 1968 said storage core, is lower than the minimum value which the said current must take in order to -produce this reversal.

Various objects, features and advantages of the present invention will become apparent from the following description and from the accompanying drawings, in which:

FIGURE 1 diagrammatically illustrates a shift register according to the invention;

FIGURE 2 is a curved diagram representing the operation of the shift register illustrated in FIGURE 1;

FIGURE 3 contains the curves representing the hysteresis loops of magnetic substances from which the magnetic cores of the register may be formed, and

FIGURE 4 contains the curves representing certain relations which must exist, in accordance with one feature of the invention, between certain quantities which are to be taken into consideration in the choice of the dimensions and the magnetic characteristics of the magnetic cores of the register.

FIGURE 1 illustrates four stages I, II, III and IV of a shift register according to the invention. These stages of which the reference numeral indicates the ordinal number in the register, are of like form, because they perform identical functions at different instants of the operation of the register, and the identical component elements of these stages are denoted in the present description by the same letter followed by a numeral indicating the ordinal number of the stage to which they belong.

For example, stage I comprises a magnetic storage core M1, a magnetic transfer core T1, input windings E1 and S1 respectively and a shift control winding D2, the said windings being supported by the magnetic core, transfer and neutralising windings L1 and M1 respectively supported by the transfer core, and a transfer circuit Trl comprising the windings S1, L1 and E2 connected in series, and having a resistance R1 other than zero.

The number of turns of the winding S1 is greater than that of the Winding E1.

In addition, the register comprises shift control circuits da, db and dc, neutralisation control circuits na, nb and nc, current sources A, B, C supplying respectively shift control currents Ia, Ib, Ic to the circuits da, db, dc, and current sources NA, NB, NC supply neutralisation control currents Ina, Infb, Inc respectively to the circuits na, nb, nc. The instants of application and the duration of these currents during the shift operations are indicated by FIGURE 2, the successive shift operations P0, P1, P2, etc. commencing at instants denoted by the successive symbols t0, t1, t2, etc., respectively.

The storage cores are made of a substance which has a considerable residual induction. More particularly, they may be made of a substance having the hysteresis loop represented in FIGURE 3 by the solid-lined curve.

The values b0 and b1 of the residual induction B of a storage lcore represent, during the operation of the register, the binary values ZERO and ONE respectively.

In FIGURE 1, a dot has been placed close to one end of each winding of the storage cores to indicate that a current entering the winding through the end thus marked tends to bring the core supporting this winding to the state of residual induction chosen to represent the binary value ZERO.

The transfer cores are made of a substance having a low residual induction. More particularly, they may be made of a substance having the hysteresis loop represented in FIGURE 3 by the chain-line curve, their dimensions (cross-section and mean circumference) being so chosen that certain conditions indicated in the following are satisfied. In order to satisfy these conditions, the transfer cores may have, for example, the same cross-section as the storage cores, but a smaller length, or they may have the same length as the latter, but a larger cross-section.

A portion of the magnetic circuit of each transfer core isl divided by an aperture into two parallel branches of like Section 11 and 12, and the neutralisation winding supported by a transfer core enters this aperture in the core so as to surround only one of the said parallel branches of the said core.

The neutralisation currents flowing in such a winding have sufficient strength to bring these branches 11 and 12 to magnetic saturation, and they then have the effect of -cancelling the flux and thus opposing any variation of ilux throughout the cross-section of the core.

In order to explain the operation of the shift register which has just been described, reference will now be made to the shift operation P4 (FIGURE 2), and it Will be assumed that at the instant t4 the storage core M2 of the stage II is in a state ONE, while the storage cores of the other stages are in the state ZERO, and that the magnetic induction in the transfer cores is ZERO or negligible.

At this instant t4, a current Ib and a current Inb commence to flow through the windings D2 and N2 respectively, while a current Ia, which as been set up at the preceding instant t3, and which lasts until the next instant t5, flows through the windings D1 and D4 of the magnetic cores M1 and M4 respectively. This current Ia has the effect of maintaining the cores M1 and M4 in the ZERO state and of opposing and flux variation in these cores until the instant t5. The current Inb has the effect of opposing any ilux variation in the core T2. Finally, the current Ib has the effect of changing the magnetic state of the core M2 and bringing it from the state ONE to the state ZERO.

The reversal of the direction of the residual induction in the core M2 produces a flux variation through the turns of the windings E2 and S2 of the said core, and an induced electromotive force is set up at the ends of these windings.

The electromotive force set up at the ends of the winding E2 generates a current in the transfer circuit Trl which comprises the series-connected windings S1, L1 and E2. This lcurrent should preferably remain fairly low in order that the reversal of the direction of the residual induction in the core M2 may not be accompanied by an excessive dissipation of energy.

During the establishment of this current, the magnetic induction in the core T1 changes from the value O to a value B1 (FIGURE 3), so that the Winding L1 sets up a counter-electromotive force opposing the passage of this current. The winding S1, on the other hand, does not set up any counter-electromotive force to this current owing to the fact that the flux and the core N1 is maintained at a constant value by the current Ia in the winding D1. Finally, the voltage drop across the resistance of the circuit Trl may, as a first approximation, be regarded as negligible, because the value of this resistance R1 is sufficiently small to avoid attenuation of the transmitted signals in the signal transfers through the circuit Trl. It is therefore mainly by means of the counter-electromotive force set up by the winding L1 that the current then flowing through the circuit Trl can be limited. The dimensions of the transfer core T1 and the magnetic characteristics of the substance forming the latter must therefore be so chosen that this result is obtained.

While the reversal of the direction of the residual induction in the core M2 is taking place, the electromotive force induced in the winding E2 commences to decrease. The current through the circuit Tf1 then tends to decrease, and the induction in this core T1 tends to be cancelled out, so that, at the ends of the winding L1, there is set up an electromotive force which tends to maintain the current in the circuit Trl. Owing to the fact that the resistance of the circuit Trl is not zero, vthis current decreases sufficiently before the instant t5V for the magnetic induction in the core T1 to be, at this instant, below a given appropriate value and to be unable to disturb the operation of the register in the succeeding shift operation.

At the reversal of the direction of theresidual induction in the core M2, at the instant t4, the electromotive force set up at the ends of the winding S2 generates a current in the transfer circuit Tr2 Which is formed of the series-connected windings S2, L2 and E3.

The winding L2 'does not set up any counterelectromotive force to this current, because no flux variation can occur in the core T 2 between the instants t4 and t5 owing to the passage of the neutralising current Inb through the winding N2 of this core between these instants. f

Moreover, the circuit Tr2 is so constructed as to have a sufficiently low resistance to avoid an attenuation of the signal which it transmits.

The current flowing through the winding E3 then tends to bring the core M3 to a state ONE.

The electromotive force set up at the ends of the winding S3 as a result of the reversal of the direction of the residual induction in the core M2 generates a current'in the transfer circuit Tr3. This current must remain suiciently low in relation to the current flowing through the transfer circuit Tr2 to enable the reversal of the direction of the residual induction in the core M3 to take place.

During the establishment of this current, the magnetic induction in the core T3 changes from the Zero value to a value B1 (FIGURE 3), so that the winding L3 sets up a counter-electromotive force to the passage of this current. The winding E4, on the other hand, does not set up any counter-electromotive force to this current, because the latter tends to maintain in the ZERO' state the core M4 which is already maintained in this ZERO state by the current Ia. Finally, the voltage drop due to the resistance of the circuit Tr3 may be regarded as negligible, because the value R3 of this resistance must be made sufficiently low for the reason indicated in the foregoing with refer.

ence to the transfer of information which takes place through the circuit T r2. It is therefore mainly by-means of the counter-electromotive force set up by the winding L3 that the current then flowing through the circuit Tr3 can be limited. The dimensions of the transfer core T3 and the magnetic characteristics of the latter must therefore be so chosen as to give the self-inductance of the transfer circuit Tr3 a sufficiently high value.

While the current flowing through the circuit Tr2 is being established, the electromotive force induced in the winding S3 starts to decrease, so that the current flowing through the circuit Tr3, and consequently the magnetic induction in the core T3, tends to decrease. An electromotive force which tends to maintain the current in the circuit Tr3 is then set up at the ends of the winding L3. This current, which is necessarily below the value which it should have in order to maintain in the core T3 the magnetic induction of value B1 which has been obtained in this core when the electromotive force has been set up at the ends of the winding S3, must remain lower than the threshold current from which the core M3 is returned to the ZERO state.

This condition is satisfied if thedimensions of the transfer core T3 and the magnetic characteristics of the substance forming this core are so chosen that the current capable of producing in the core T3 a magnetic induction of .value equal to the value B1 obtained in this core at the instant T4 is lower than the threshold current under consideration.

There have been `shown in FIGURE 4 characteristic curves @s (IS) and @L (IL) showing the relations which must exist, in order to satisfy the aforesaid condition, between the values of the flux @s through the turns of the Winding S3, of the current Is in this winding, of the flux @L through the turns of the winding L3 and of the current IL in this winding. In FIGURE 4, the value I1 of the current IL is that which determines through the turns of the winding L3 a ux @l equal to the flux variation dos which results, through the turns of the winding S3, from the reversal of the direction of the residual induction in the storage core M3, the threshold value I2 of the current IS being the minimum value which this current must have in order to produce this reversal of the direction of the residual induction in the core M3, while the characteristic curves shown are such I1 is lower than I2.

The curves shown in FIGURE 4 permit of determining the respective dimensions and magnetic characteristics of the storage cores and of the transfer cores of a shift register according to the invention when the latter is to operate in the manner indicated in the foregoing.

It will be observed that the shift register just described may function by means of control pulses whose duration is similar to the change-over duration of the storage cores, that is to say, by means of current pulses which are substantially shorter than those whose duration `is indicated in FIGURE 2.

The magnetic cores of a shift register according to the invention may advantageously be formed of thin magnetic films having an axis of easy magnetisation. The rectangular' hysteresis loop possessed by such a lm with respect to the magnetomotive forces directed along the axis of easy magnetisation are utilised to obtain the operation of the storage cores, while the linear hysteresis loop pos sessed by this film perpendicularly to the axis of easy magnetisation is utilise-d for the operation of the transfer cores.

Although it has been stated in the foregoing description that the transfer cores have negligible residual induction, shift registers according to the invention may also be constructed with transfer cores having a non-negligible residual induction. The residual induction which the transfer core then acquires in the course of a transfer operation has the effect of producing an attenuation of the signal transferred in the course of the succeeding transfer operation. This attenuation may be compensated for by increasing the turns number ratios of the output windings and of the input windings of the storage cores.

We claim:

1. In a three coresper-bit magnetic core shift register,

a plurality of storage magnetic cores of high residual flux density material arranged in a sequence and successively designated as SA, SB and SC, in each group of three successive cores provided for each binary bit of information,

an input winding, an output winding `and a drive winding on each of said storage cores,

a transfer circuit associated with each of said storage cores, said transfer circuit comprising an auxiliary magnetic core of low residual flux density material having a main aperture and a secondary aperture,

a transfer winding wound through the main 'aperture of the auxiliary magnetic core,

an inductance control winding wound through the secondary aperture of the auxiliary magnetic core,

and circuit means connecting the transfer Winding in series with the `output winding of the storage core to which the transfer circuit is associated and with the input winding of the next succeeding storage core,

means for separately generating three drive pulse trains designated as Ia, Ib and Ic, having the same pulse recurrence frequency, a phase shift of a third of a cycle with respect to each other, and a pulse duration-to-pulse interval ratio larger than one, means for separately generating three inductance control pulse trains designated as Ina, Inb and Inc, in phase with the drive pulse trains Ia, Ib and Ic respectively, and having a pulse: duration-to-pulse interval ratio equal to one-half, means for applying the pulse trains Ia, Ib and Ic to the drive windings of the storage cores SA, SB and SC respectively, and means for applying the pulse trains Ina, Inb and Inc to the inductance control windings comprised in the transfer circuits associated with the storage cores SA, SB and SC respectively, application of an inductance control pulse to the inductance control winding of an auxiliary core preventing flux variation through such au auxiliary core, and the operating characteristics of the storage cores and of the auxiliary cores being so adapted that the value of the current which is equal to the liux change obtained in a storage core as the latter switches from one to the other of its stable states of residual flux, is less than the minimum value of the current which is necessary for bringing about a change in the flux state of the storage core.

2. In a three coresper-`bit magnetic core shift register, in combination:

a plurality of storage magnetic cores of high residual flux density material arranged in a sequence, an input winding, an output winding and a drive `winding on each of said storage cores, a transfer circuit associated with each of said storage cores, said transfer circuit, comprising an auxiliary magnetic core of low residual flux density material having a main aperture and a secondary aperture, a transfer winding wound through the main aperture of the auxiliary magnetic core, an inductance control winding wound through the secondary aperture of the auxiliary magnetic core, and circuit means connecting the transfer winding in series with the output winding of the storage core to which the transfer circuit is associated, and with the input winding of the next succeeding storage core, the operating characteristics of the storage cores and of the auxiliary cores being so adapted that the value of the current which is necessary for establishing in an auxiliary core a flux which is equal to the flux change obtained in a storage core as the latter switches from one to the other of its stable states of residual ux, is less than the minimum value of the current which is necessary for bringing about a change in the flux state of the storage core.

References Cited UNITED' STATES PATENTS 2,781,503 2/1957 Saunders 340-174 2,907,957 10/1959 Dewitz 340-174 2,907,987 10/1959 Russell 340-174 2,918,664 12/1959 Bauer 340-174 2,974,311 -3/ 1961 Kauffmann 340-174 3,077,585 2/1963 Butler 340-174 3,083,355 3/1963 Engelbart 340-174 3,112,409 11/ 1963 Engelbart 307-88 3,157,794 11/1964 Kahn 307-88 3,192,511 6/1965 Dick V340-174 3,204,225 8/ 1965 Branley et al. 340-174 STANLEY M. URYNOWICZ, I R., Primary Examiner. 

1. IN A THREE CORES-PER-BIT MAGNETIC CORE SHIFT REGISTER, A PLURALITY OF STORAGE MAGNETIC CORES OF HIGH RESIDUAL FLUX DENSITY MATERIAL ARRANGED IN A SEQUENCE AND SUCCESSIVELY DESIGNATED AS SA, SB AND SC, IN EACH GROUP OF THREE SUCCESSIVE CORES PROVIDED FOR EACH BINARY BIT OF INFORMATION, AN INPUT WINDING, AN OUTPUT WINDING AND A DRIVE WINDING ON EACH OF SAID STORAGE CORES, A TRANSFER CIRCUIT ASSOCIATED WITH EACH OF SAID STORAGE CORES, SAID TRANSFER CIRCUIT COMPRISING AN AUXILIARY MAGNETIC CORE OF LOW RESIDUAL FLUX DENSITY MATERIAL HAVING A MAIN APERTURE AND A SECONDARY APERTURE, A TRANSFER WINDING WOUND THROUGH THE MAIN APERTURE OF THE AUXILIARY MAGNETIC CORE, AN INDUCTANCE CONTROL WINDING WOUND THROUGH THE SECONDARY APERTURE OF THE AUXILIARY MAGNETIC CORE, AND CIRCUIT MEANS CONNECTING THE TRANSFER WINDING IN SERIES WITH THE OUTPUT WINDINGS OF THE STORAGE CORE TO WHICH THE TRANSFER CIRCUIT IS ASSOCIATED AND WITH THE INPUT WINDING OF THE NEXT SUCCEEDING STORAGE CORE, MEANS FOR SEPARATELY GENERATING THREE DRIVE PULSE TRAINS DESIGNATED AS IA, IB AND IC, HAVING THE SAME PULSE RECURRENCE FREQUENCY, A PHASE SHIFT OF A THIRD OF A CYCLE WITH RESPECT TO EACH OTHER, AND A PULSE DURATION-TO-PULSE INTERVAL RATIO LARGER THAN ONE, MEANS FOR SEPARATELY GENERATING THREE INDUCTANCE CONTROL PULSE TRAINS DESIGNATED AS INA, INB AND INC, IN PHASE WITH THE DRIVE PULSE TRAINS IA, IB AND IC RESPECTIVELY, AND HAVING A PULSE DURATION-TO-PULSE INTERVAL RATIO EQUAL TO ONE-HALF, MEANS FOR APPLYING THE PULSE TRAINS IA, IB AND IC TO THE DRIVE WINDINGS OF THE STORAGE CORES SA, SB AND SC RESPECTIVELY, AND MEANS FOR APPLYING THE PULSE TRAINS INA, INB AND INC TO THE INDUCTANCE CONTROL WINDINGS COMPRISED IN THE TRANSFER CIRCUITS ASSOCIATED WITH THE STORAGE CORES SA, SB AND SC RESPECTIVELY, APPLICATION AND AN INDUCTANCE CONTROL PULSE TO THE INDUCTANCE CONTROL WINDING OF AN AUXILIARY CORE PREVENTING FLUX VARIATION THROUGH SUCH AN AUXILIARY CORE, AND THE OPERATING CHARACTERISTICS OF THE STORAGE CORES AND OF THE AUXILIARY CORES BEING SO ADAPTED THAT THE VALUE OF THE CURRENT WHICH IS EQUAL TO THE FLUX CHANGE OBTAINED IN A STORAGE CORE AS THE LATTER SWITCHES FROM ONE TO THE OTHER OF ITS STABLE STATES OF RESIDUAL FLUX, IS LESS THAN THE MINIMUM VALUE OF THE CURRENT WHICH IS NECESSARY FOR BRINGING ABOUT A CHANGE IN THE FLUX STATE OF THE STORAGE CORE. 